The present invention relates to a hot plate unit, and more particularly, to a hot plate unit used to heat silicon wafers during a semiconductor manufacturing process.
During a semiconductor manufacturing process, for example, when heating and drying a silicon wafer subsequent to the application of a photosensitive resin, a heating apparatus, which is normally referred to as a hot plate unit, is used.
For example, Japanese Examined Patent Publication No. 4-13837 describes a prior art example of such apparatus. The heating apparatus of the publication includes a hot plate, which functions as an electric heating member and is made of sintered aluminum nitride, and a resistor, which is arranged in the plate. The resistor is held between ceramic base materials, which form the hot plate. The resistor has two ends that project from the side of the hot plate and are connected to a power supply via a power line.
A silicon wafer, which is a heated subject, is placed on an upper surface of the hot plate. When the resistor is energized in this state, the silicon wafer is heated to a predetermined temperature (e.g., several hundred degrees).
When the resistor is energized for a predetermined time to dry photosensitive resin, the hot plate is first cooled to a relatively low temperature. Then, the silicon wafer is removed from the hot plate. However, a relatively long time is necessary for the cooling. This limits productivity.
Thus, for example, a cooling pipe through which a coolant flows may be arranged on the lower surface of the plate to forcibly cool the plate and shorten the cooling time. However, this not only causes the entire unit to have a complicated structure but also causes the unit to be bulky and large.
Further, air may be forced against the lower surface of the hot plate to cool the plate and shorten the cooling time. However, this may contaminate the periphery of the apparatus with moisture and dust that are included in the air.
It is an object of the present invention to provide a hot plate unit that cools within a relatively short period of time without a complicated or enlarged structure.
A perspective of the present invention proposes a hot plate unit, which is arranged in an opened portion of a casing and has a resistor. A space for enabling the circulation of fluid is formed by the casing and the hot plate and an inner bottom plate is provided in the casing.
It is preferable that an opening be formed in the inner bottom plate.
In the present inventions a fluid circulates in the space formed by the casing and the hot plate. This enables forced cooling of the hot plate and shortens the cooling time in comparison to natural cooling. Further, since cooling pipes are not required, there is no need for concern of the Structure of the entire unit becoming complicated or bulky.